Glass Composite Fiber for Broadband NIR‐II Mini Light Source

Abstract Near‐infrared second window (NIR‐II, 1000–1700 nm) light sources present remarkable scientific and technological promise, with wide‐ranging applications spanning biomedical imaging, biosensing, and related fields. However, most of the available candidates are in bulk form and it is urgently required to develop mini light sources. Herein, a broadband NIR‐II mini fiber‐type light source equipped by Ni 2+ activated glass composite fibers is proposed and investigated. It is shown that the transparent glass composite exhibits broadband NIR‐II emission with a full width half‐maximum approaching 240 nm and an internal quantum efficiency (IQE) larger than 50% by rational control of nanocrystallization. Additionally, the corresponding glass composite fibers are prepared, demonstrating efficient broadband response and distinct on‐off gain in NIR‐II region. Benefited from above features, an all‐fiber mini light source by fusing glass composite fibers with commercial passive fibers is successfully constructed and demonstrates its promising applications for NIR‐II imaging. These findings demonstrate significant progress in the development of NIR‐responsive photonic materials, enabling advanced applications in photonic technology.